The irons for ironing clothes are provided with a soleplate, which is the element that slides on the fabric while heating it. Such irons often comprise a steam generator, in which case the soleplate comprises some steam outlets.
The soleplate's outer surface should slide smoothly on the fabric, and the soleplate should cope with both high temperatures and sudden changes of temperature. Moreover, the soleplate should be resistant to blows and scratches.
Conventional irons have a metallic soleplate, normally made of an aluminium substrate coated (on the ironing side) with a layer of stainless steel, anodized aluminium or enameled aluminium. The soleplate is heated by heating elements usually in the form of electric resistances embedded in the soleplate. Such resistances have normally a tubular shape, so that they can be bent but with a minimum radius that is quite large.
Such conventional irons present, among others, the following drawbacks: the stainless steel coating is scratched with use, the soleplate is heavy, the heat distribution in the soleplate is not uniform, the resistances are large and impose limitations on the soleplate's geometry, the heat transmission from the aluminium to the stainless steel is bad and must be helped by using conductive pastes.
Metallic soleplates with embedded resistances coated with a glass-ceramic material are known too. Glass-ceramics materials are very hard and present high thermal and mechanical resistance.
Spanish patent No. 456442 discloses an iron's soleplate made of a thick inner plate having slanted surfaces which face each other and can be moved to fasten the soleplate to the iron's case, and a thinner outer plate welded to the inner plate. The resistances are embedded between the two plates and the plates can be made of, among others, a glass-ceramic material.
PCT application No. WO 93/02533 discloses an iron's soleplate consisting of a metallic substrate coated with a glass-ceramic material on both sides. Heating tracks are arranged on the inner side; said tracks contain platinum or any conductive material the electric conductivity of which conveniently decreases when increasing the temperature, thus providing a thermal self-control.
By using the soleplate's configuration disclosed in these documents, the heat must pass through several layers of materials having different thermal properties (heating capacity, thermal expansion, etc), thus making difficult the heat transmission and making likely the formation of cracks. Besides, the need to house so much material rests space for other elements of the iron and makes it heavy.